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Tue, 24 Mar 2026 01:01:11 +0000 Message-ID: <84489fd4-aa23-4ba1-b5a1-c1baafb6718d@intel.com> Date: Mon, 23 Mar 2026 18:01:09 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] x86/fred: enable FRED by default Content-Language: en-US To: "H. Peter Anvin" , Thomas Gleixner , "Ingo Molnar" , Borislav Petkov , Dave Hansen , CC: "Peter Zijlstra (Intel)" , Kees Cook , Xin Li , "Ahmed S. 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Peter Anvin wrote: Can we please include this as well? diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c index e736b19e18de..117aa06d25ca 100644 --- a/arch/x86/kernel/fred.c +++ b/arch/x86/kernel/fred.c @@ -27,9 +27,6 @@ EXPORT_PER_CPU_SYMBOL(fred_rsp0); void cpu_init_fred_exceptions(void) { - /* When FRED is enabled by default, remove this log message */ - pr_info("Initialize FRED on CPU%d\n", smp_processor_id()); - /* * If a kernel event is delivered before a CPU goes to user level for * the first time, its SS is NULL thus NULL is pushed into the SS field > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 03a550630644..bfa8a20ccc37 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1750,8 +1750,8 @@ Kernel parameters > fred= [X86-64] > Enable/disable Flexible Return and Event Delivery. > Format: { on | off } > - on: enable FRED when it's present. > - off: disable FRED, the default setting. > + on: enable FRED when it's present, the default setting. Why do we need the fred=on line after this series? It can't really enable FRED when the compile option is disabled. Seems like a dead (and slightly confusing) option to me. > + off: disable FRED. > > ftrace=[tracer] > [FTRACE] will set and start the specified tracer > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index e2df1b147184..876b663dcf38 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -557,7 +557,7 @@ config X86_FRED > bool "Flexible Return and Event Delivery" > depends on X86_64 > help > - When enabled, try to use Flexible Return and Event Delivery > + When enabled, use Flexible Return and Event Delivery > instead of the legacy SYSCALL/SYSENTER/IDT architecture for > ring transitions and exception/interrupt handling if the > system supports it. > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index a8ff4376c286..e22a49869380 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1746,7 +1746,7 @@ static void __init cpu_parse_early_param(void) > > /* Minimize the gap between FRED is available and available but disabled. */ > arglen = cmdline_find_option(boot_command_line, "fred", arg, sizeof(arg)); > - if (arglen != 2 || strncmp(arg, "on", 2)) > + if (arglen > 0 && (arglen != 2 || strncmp(arg, "on", 2))) > setup_clear_cpu_cap(X86_FEATURE_FRED); Nit: Would it be better to compare with "off" rather than not on? > > arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));